tanker trio

Tanker trio streamlines the waterline

Heading below the waterline allowed Wärtsilä engineers to redesign its Aframax hull, increasing flow to the propeller and improving efficiency. Several green-tech touches completed the makeover, which created a splash at the tanker launch at Posidonia.

Text: PATRICK REILLY Photo: WÄRTSILÄ

Putting a new spin on the Aframax concept is no easy feat. After all, the AFRA (Average Freight Rate Assessment) system has been around since the 1950s and remains the standard bearer for medium-sized crude tankers. 

But that is exactly what Wärtsilä is aiming to do with its latest Aframax tanker design, available in not one, not two, but three different configurations; basic, environmental and dual-fuel. Going green is the motivating force behind the trio of ships with the caveat that efficiency gains shouldn’t compromise performance. 

Plans for the new breed of ships were on the drawing board as long ago as 2011. Growing pains were inevitable as the challenges of creating a modern Aframax prompted the designers to have a rethink, but the perseverance has paid off with interest already high in the fleet. 

“Our initial concept was not really competitive in terms of efficiency so we went back to the drawing board and focused more on the underwater structure of these ships. Our efforts to improve the hull lines on this specific design are unparalleled compared with anything we have done before,” says Jacob Høgh Thygesen , Head of Merchant Ship Design Solutions with Wärtsilä. 

The process involved extensive use of CFD (computational fluid dynamics), a proven and widely used method in the ship design business, and tank testing with the Force Institute in Copenhagen to further evaluate the merits of all three designs. 

“Getting the optimum flow to the propeller is vital, so to do that we lifted the stern significantly. Compared to the first design in 2011 the underwater profile of the ship now is quite different. As a result we improved the efficiency level by more than 25% compared to the first one,” Thygesen adds. 

Established in 1954 by Shell, the Aframax is one of the most iconic oil tankers. Not to be confused with a supertanker, an Aframax vessel is smaller than 120,000 tonnes with a maximum width of the Panama Canal – 32.2 metres.

tanker trio 2
DUE TO ITS DIMENSIONS AN AFRAMAX SHIP IS IDEAL FOR SERVING ROUTES THAT DON’T HAVE LARGE PORTS.

Due to its dimensions an Aframax ship is ideal for serving routes that don’t have large ports. Which is just what these lengthy vessels have been doing for the past six decades; the average transport capacity is 700,000 barrels of crude oil in cargo. 

The global demand for oil is as strong as ever, but recent environmental legislation means the transport of black gold has to be greener and cleaner. What was de rigueur 10, or even five years ago is no longer acceptable, which prompted Wärtsilä to take a three-pronged strategy to its new fleet. 

At the launch of the new Aframax design at the Posidonia 2014 exhibition in Greece this summer, Wärtsilä executives revealed the much-anticipated trio of tankers. 

The basic configuration runs on heavy fuel oil, the environmental model has the exhaust emissions cleaned using a scrubber and selective catalyst reduction, while the green version runs on dual-fuel engines. 

“For all intents and purposes it is the same ship. If you compare the conventional version to the green model there is a reduction in energy consumption by roughly 10%. Our fuel oil version is already in a different class when it comes to efficiency so that means the dual-fuel version is even more attractive to buyers,” says Thygesen. 

Key to those energy gains has been the rigorous attention devoted to the ship’s hull.

“When you have ships with a high block coefficient, in the sense that there is a very large surface beneath the water line when it is fully loaded, the hull lines are extremely important for any efficiency gains. After a complicated and lengthy process we found a successful way of applying a method to get the ship to perform how it does.” 

Furthermore, the aerodynamics of the vessel were tested using CFD, which improved the accommodation profile and yielded more gains. 

Thygesen adds; “By doing this it gave us 0.3 tonnes per day in improved efficiency.” 

The new Aframax has a dead weight of 111,000 metric tonnes an endurance of seven days at sea (approximately 6,000 miles) and is capable of operating at a speed of 14.5 knots. Fuel oil consumption is estimated to be 35.2 tonnes per day with power provided by a two-stroke Wärtsilä 6X62 main engine. 

Wärtsilä’s new addition to the sector comes at a good time as the AFRA market has seen a spike in rates throughout 2014. The first vessels are expected to come onstream in late 2016 and largely operate in the Black Sea, North Sea, South and East China Seas and the Mediterranean. 

Thygesen says that Wärtsilä is in “very close talks” with a number of serious owners. A brand new Aframax will cost in the region of $50–$55 million. Wärtsilä is also offering shipyards integration packages in order to make it possible for more builders to get active in this specialist market. 

Knowing the needs of the shipowners was made easier by teaming up closely with global shipping giant Clarksons in London. 

“That provided us with a huge know-how of what the owners are faced with, such as the optimum size, potential operational barriers and so on. On the surface it may seem insignificant but if they are operating 10 ships over a 25-year period running 365 days a year, we need to know their market drivers and models,” Thygesen adds. 

The same high standards apply when it comes to remaining true to Wärtsilä’s core principles

“We have a very significant obligation to the brand of Wärtsilä. That comes at a cost, of course, but we believe from an ethical and moral point of view it is the right approach.” 

An approach that looks set to pay dividends, judging by the amount of curiosity the new Aframax has aroused in shipowners.

“In the Aframax sector we are extremely proud to have the most fuel-efficient design. This is the way forward and it is only a matter of time before the merchant fleet gets onboard also,” concludes Thygesen.

 

Press release

Wärtsilä Ship Design

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